The use of coiled tubing injectors for drilling oil and gas well has risen dramatically in recent years. More particularly, the use of coiled tubing injectors in the use of directional drilling has gained widespread acceptance.
In the drilling of vertical, directional, or horizontal wells, there is a need for accurately controlling the weight on the drill bit (WOB). Accurate control of WOB is particularly critical when either directional or horizontal wells are being drilled. In directional or horizontal wells, the weight on the drill bit affects the angular deviation of the drill hole away from the vertical. By obtaining an accurate time measurement of the duration of travel of the rotary bit within the well bore, together with providing a way of accurately limiting the loads that are placed on the drill bit, it is possible to execute delicate and sophisticated drilling operations while minimizing downhole tool failures and maximizing the life of the drill bits.
U.S. Patent Publication 2008/0296013 ('013 Publication), incorporated herein by reference for all purposes, discloses a top mounted injector for coiled tubing injection comprising an injector supported from a mounting component in a support system e.g. a mast, the mounting component including a carrier which is engageable with the mast for transferring to the mast the forces exerted on the mounting component from the injector component during the injection and withdrawal of tubing by the injector component. The '013 Publication discloses a strain gauge deployed between the injector and the mounting component for providing continuing indication of the forces developed in injecting or withdrawing the tubing from the borehole and consequently the force transferred between the injector to the mast through the mounting component. However, in the arrangement shown in the '013 Publication, vis-à-vis determining accurate WOB, the arrangement in the '013 Publication suffers from the fact that the injector is suspended via one strain gauge and a hinge.